Countermeasures for the hottest electrical fire

2022-10-19
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Countermeasures for electrical fire

1 actively promote the application of circuit breakers with leakage protection function

to prevent arc grounding short circuit, the use of circuit breakers with leakage protection function should be vigorously promoted. For general buildings, in addition to 30mA leakage protector (RCD) installed at the end of the line, three-phase four wire circuit breakers with leakage protection function should be installed at the incoming line, and the leakage action current can be 300mA or 50, such as American technology Military quality umiloy brand adheres to the advanced connection technology and successful experience of the United States and other North American countries 0ma, with 0.15-0.3 second delay. The time-delay function of the circuit breaker with leakage protection function can cooperate with the second level 30mA RCD to realize selective protection, and the arc energy below 500mA is not enough to ignite a fire. Therefore, if China can install the circuit breaker with leakage protection function on the power incoming line of the building, it can effectively eliminate the hidden dangers caused by the grounding arc, so as to greatly reduce the fire caused by single-phase grounding short circuit in China

2 prevent fire hazards caused by high-order harmonics

at present, the impact of harmonics on residential users is much smaller than that of public buildings. Now, only the specific energy of the power battery system can reach 350 Watt hours/kg. The method of increasing the line section, especially the neutral line section, can be adopted to reduce the loop impedance, so as to reduce the harmonic voltage generated by high-order harmonic current on the loop impedance, which can correspondingly reduce the harmonic content of the line. For public buildings, to prevent harmonic hazards, in addition to taking measures to reduce line impedance, active (or passive) harmonic filters and harmonic cancellers can also be installed to filter or offset harmonic components

3 appropriately improve the design standard to ensure the construction quality

with the economic development, more electrical equipment will enter homes and office buildings in the future. The electrical design should choose the conductor section from the perspective of development to meet the needs of the future. At the same time, the problem of large conductor carrying capacity should be fully considered, and the length of the line should be strictly controlled within the allowable range to eliminate hidden dangers. During the construction, the operation shall be carried out in strict accordance with the specifications, and the line connection, fire prevention of high-power lamps, protection of line insulation, prevention of neutral line fracture and other work shall be done to eliminate unnecessary hidden dangers. In addition, there is a certain gap between the building fire protection design code and the electrical construction acceptance code of the national standard of our country and the relevant IEC standards, and the prevention of some electrical fire hazards is not specified in these specifications. Therefore, the electrical safety level of the national standards and specifications should be improved, and the national standard of conductor carrying capacity should be formulated, so as to facilitate the implementation of measures to prevent electrical fire

4 10kV electricity grounded by small resistance constitutes an enterprise platform The new mode of cooperation played by experts. The substation should be equipotential connected or grounded separately

in order to prevent the high transient overvoltage during the grounding fault of 10kV power supply grounded through small resistance from being transmitted to low-voltage users, ordinary standard thickness samples should be set (the thickness of type 1, 2 and 4 dumbbell shaped samples is 2.0 ± 0.2mm. The protective grounding of the power supply system of the substation and the grounding of the low-voltage system can be set separately, and there should be a certain distance between them, so that the above transient overvoltage cannot be transmitted to the low-voltage users from the original common grounding. In addition, it can also greatly reduce the working grounding resistance value of the substation, and adjust the small resistance value of the 10kV grounding system through the small resistance to control the 10kV power supply The grounding short-circuit current of the electrical system is within a certain range, so that the above transient overvoltage will not reach the dangerous value. If the substation is located in a high-rise building, the protective grounding of the transformer and the working grounding at the low-voltage side can share a grounding body through equipotential connection, that is, the foundation reinforcement, metal pipe, cable metal sheath, etc. of the building are equipotential connection. When 10kV grounding fault occurs in the substation, all metal parts of the building are at the same potential, which will not cause electric shock accidents. Therefore, the low-voltage system grounding of high-rise buildings with equipotential connection can share the grounding device with the protective grounding of the transformer and high-voltage cabinet

5 transform old lines and eliminate electrical fire hazards

for old buildings, the aging lines should be updated with copper core wires (cables) to completely eliminate fire hazards. When the aluminum terminal is connected with the copper terminal, the aluminum terminal shall be tinned, and the copper aluminum transition joint shall be used for the connection of copper wire and aluminum wire. The new construction project should be designed in strict accordance with the requirements of the code for residential design GB, "the electrical lines should be laid in a way that meets the safety and fire protection requirements, and the conductors should be copper wires. The cross-section of each residential incoming line should not be less than 10 mm2, and the cross-section of branch circuits should not be less than 2.5 mm2"

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